There have been developed diagnosis devices for abnormal sounds of electric apparatuses. For example, PCT International Publication No. 2015/068446 discloses an abnormal sound diagnosis device which obtains a time-frequency distribution by spectral analysis of an operating sound to be diagnosed, detects a specific component defined in advance from the time-frequency distribution, counts the number of detection of the specific component in the time-frequency distribution, and compares a specific component count value during normal operation and a specific component count value at the time of diagnosis to determine an increase not less than a set value to be abnormal.
As after-sales service of common home electrical appliances, some technical staffs are dispatched to houses of users of home electrical appliances to diagnose abnormal sounds of the home electrical appliances. On this occasion, various interference sound sources (noises) are inevitable in the users' houses. When a technical staff diagnoses an abnormal sound of a home electrical appliance at a user's house by using the abnormal sound diagnosis device disclosed in PCT International Publication No. 2015/068446, an interference sound source, if present, causes reduction in diagnosis precision of an abnormal sound by the abnormal sound diagnosis device. Therefore, it is demanded to reduce influences of an interference sound source as much as possible.
Regarding the problem, for example, Japanese Unexamined Patent Application Publication No. 2006-60720 discloses a sound collection system which emphasizes and records a sound from a target sound source under the presence of an interference sound source. According to the technique disclosed in Japanese Unexamined Patent Application Publication No. 2006-60720, at least one microphone collects a sound while rotating around a rotational shaft to conduct filter processing corresponding to positional information of the microphone at each time point. This enables removal of a sound from an interference sound source, as well as enabling a sound from a target sound source to be emphasized and recorded.
The above-described conventional technique, however, needs a mechanism for rotating at least one microphone, so that further improvement is required.